Information storage devices typically include an air bearing slider assembly for reading and/or writing data onto the storage medium, such as a disk within a rigid disk drive. An actuator mechanism is used for positioning the slider assembly at specific locations or tracks in accordance with the disk drive usage. Linear and rotary actuators are known based on the manner of movement of the slider assembly. Head suspensions are provided between the actuator and the slider assembly and support the slider assembly in proper orientation relative to the disk surface. Head suspensions of this type are commonly manufactured by chemically etching flat or unformed load beam blanks from thin sheets of stainless steel.
In reaction to the moving air at the surface of the spinning disk, the slider assembly develops an aerodynamic force which causes the slider assembly to lift away from and “fly” over the disk surface. In order to establish the fly height, the head suspension is also provided with a spring force counteracting the aerodynamic lift force. The height at which the slider assembly flies over the disk surface is known as the “fly height.” The force exerted by the suspension on the slider assembly when the slider assembly is at fly height is known as the “gram load.”
An important performance-related criteria of a suspension is specified in terms of its resonance characteristics. In order for the slider assembly to be accurately positioned with respect to a desired track on the magnetic disk, the suspension must be capable of precisely translating or transferring the motion of the positioning arm to the slider assembly. An inherent property of moving mechanical systems, however, is their tendency to bend and twist in a number of different modes when driven back and forth at certain rates known as resonant frequencies. Any such bending or twisting of a suspension can cause the position of the slider assembly to deviate from its intended position with respect to the desired track. Since the head suspension assemblies must be driven at high rates of speed in high performance disk drives, it is desirable for the resonant frequencies of a suspension to be as high as possible. The detrimental effects of the bending and twisting at the resonance frequencies can also be reduced by minimizing the extent of the bending and twisting motion of the suspension (also known as the gain) at the resonant frequencies.
Common bending and twisting modes of suspensions are generally known and discussed, for example, in the Yumura et al. U.S. Pat. No. 5,339,208 and the Hatch et al. U.S. Pat. No. 5,471,734. Modes that result in lateral or transverse motion (also known as off-track motion) of the slider assembly are particularly detrimental since this motion causes the slider assembly to move from the desired track on the disk toward an adjacent track. The three primary modes that produce the transverse motion are known as the sway, first torsion and second torsion modes. The sway mode is a lateral bending mode (i.e., the suspension bends in the transverse direction along its entire length). The first and second torsion modes are twisting modes during which the suspension twists about a rotational axis that extends along the length of the suspension. The first and second torsion modes produce transverse motion of the slider assembly if the center of rotation of the suspension is not aligned with the gimbal point of the slider assembly.
Head suspensions typically include elongated and often generally triangularly-shaped load beams. Torsion and sway modes are dependent on cross-sectional properties along the length of the load beam of the head suspension. These modes are normally controlled by the design of the cross-section of the load beam, i.e., side rails, channels, and the like. It is important to design the geometries of load beams so that they either possess resonance frequencies sufficiently high to be out of the range of vibration frequencies that may be experienced in particular disk drives, or to minimize the gain caused by any such resonance frequency.
Typically, side rails are provided at the longitudinal edges of the load beam, such as by bending the edges out of the plane of the load beam. Load beams having side rails are described, for example, in U.S. Pat. Nos. 3,931,641, 4,734,805, 4,853,811, 4,933,791, 5,003,420, 5,027,240, 5,027,241, 5,079,660, and 5,081,553. Forming one or more longitudinal channels on a load beam between the longitudinal edges of the load beam are described, for example, in U.S. Pat. Nos. 5,815,348 and 5,943,774.
Constructions of load beams through partial etching process have also been developed. Such load beams are described, for example, in U.S. Patent Application 2002/0051319 and U.S. Pat. Nos. 6,219,203 and 5,812,342. U.S. Patent Application 2002/0051319 shows a load beam having recesses formed by partial etching on one side of the load beam. U.S. Pat. No. 6,219,203 discloses a load beam having a ribbed structure simultaneously etched on both sides of the load beam. U.S. Pat. No. 5,812,342 disclosed a load beam having a longitudinally distributed series of transverse trenches.
There remains, however, a continuing need for suspensions having improved resonance characteristics. In particular, there is a need for designing and manufacturing head suspension load beams having optimized resonance characteristics.